1. Field of the Invention
The invention is directed to an improved fuel injection apparatus for an internal combustion engine.
2. Description of the Prior Art
A fuel injection apparatus of the type with which this invention is concerned is known from EP 0 957 261 A1 which discloses a high-pressure fuel pump and a fuel injection valve connected to it for each cylinder of the internal combustion engine. The high-pressure fuel pump has a pump piston which the engine sets into a stroke motion and which defines a pump working chamber. The fuel injection valve has a pressure chamber connected to the pump working chamber and has an injection valve member, which controls at least one injection opening and which the pressure prevailing in the pressure chamber can move in an opening direction in order to unblock the at least one injection opening. The high-pressure fuel pump and the fuel injection valve are disposed separate from each other in the engine. The high-pressure fuel pump is provided with an electrically actuated control valve, which controls a connection of the pump working chamber and therefore of the line to a relief chamber, which function is at least indirectly fulfilled by the fuel tank. In this known fuel injection apparatus, it is disadvantageous that when the control valve is open, fuel delivered by the high-pressure fuel pump is diverted toward the fuel tank and in the subsequent intake stroke of the pump piston, this piston must aspirate the entire fuel quantity once again. This decreases the efficiency of the fuel injection apparatus. Furthermore, diverting fuel delivered by the pump piston toward the fuel tank produces pressure surges in the low-pressure system connected to it, which impairs the function and service life of the fuel injection apparatus.
The fuel injection apparatus according to the invention has the advantage over the prior art that the control valve diverts fuel into the reservoir from which fuel is drawn in a subsequent intake stroke of the pump piston so that the pump working chamber only needs to aspirate part of the fuel quantity, which is required for the filling, from the fuel tank. Furthermore, no pressure surges are produced in the low-pressure region of the fuel injection apparatus when the control valve diverts the fuel into the reservoir.
Advantageous embodiments and modifications of the fuel injection apparatus according to the invention are disclosed. In one embodiment, the reservoir has a large enough volume to contain the fuel quantity that is diverted by the control valve, even when there is a smaller fuel injection quantity and therefore a greater diverted fuel quantity. Another modification permits a flexible control of the fuel injection in that the fuel injection valve can be closed when there is high pressure in the control pressure chamber.